The present invention relates to a pumping assembly for heating and faucet water plants of the kind comprising a wet-armature motor and a centrifugal pump driven thereby, and a casing pressed to shape from metal plate that has an axially oriented collar against which bears an encircling marginal area of a partition separating a pumping space from a motor space, and which is joined by welding to an encircling marginal area of a split tube separating an armature space and a stator space.
Pumping assemblies of this nature have some shortcomings in respect of the joint between the two casings, notwithstanding whether the pump and motor casings consist of cast or plate metal. The connection is commonly established by bolting together of the casing flange in mutual contact, in which connection an uneven tightening of the screws or bolts may have the result that internally situated components of the assembly are strained and that the shaft for example may thereby be caused to jam or seize in the bearings by skewing.
Apart from the bolts as the actual connecting means, several seals also have to be provided between the casing flanges or marginal areas of the partition and split tube which are to be joined together, there being three seals as a rule, which currently represent a definite risk because they become ineffective in the course of time by being compacted and embrittled and can no longer perform their sealing function. Moreover, it is understandable that the comparatively numerous parts needed for a tight joint by means of bolts represents a comensurate expenditure in respect of costs and assembling periods.
A substantial improvement may be obtained in this respect if, in accordance with the proposal described in the prior German Patent Application No. P 32 10 762.5, the pump and motor casings are pressed from metal plate and the casing flanges projecting outwards radially at the point of connection of the casings are interwelded encirclingly, that is to say if applicable simultaneously with the marginal area or flange present thereat of the partition and of the split tube. This method could however allow other problems to arise.
Upon establishing the welded joint between the radial flanges by means of a seam produced by fusion welding by means of gas, the casing is heated not only intensively but also asymmetrically. This may possibly have the result that the split tube and the partition with the bearings situated therein undergo stressing with respect to each other so that the armature jams and that a commensurate expense will thereupon be incurred because it then becomes necessary to disassemble the parts.
It is an object of the invention to provide a joint between the components to be interwelded, which is uncomplicated, remanently tight without separate sealing means as well as producible without risk to the other components of the assembly.